The present invention is directed to an incandescent lamp that emits infrared light and a method of making such a lamp.
Incandescent lamps with tungsten filaments are commonly used in general lighting. The outer envelope of such lamps is usually glass, which is a satisfactory transmitter of the visible light generated by the tungsten filament. There are uses, however, where the preferred light is infrared instead of visible light. Glass envelopes usually used in incandescent lamps do not transmit the longer infrared wavelengths and thus these common lamps are not useful in the particular applications where infrared radiation wavelengths longer than 4 microns are the desired output from the lamp.